| 摘要 |
PURPOSE:To correct a phase shift by obtaining 1st and 2nd signals by detecting a leak current component synchronously with a low frequency signal voltage and a voltage which is phase shifted by 90 deg. from said voltage, and subtracting the product of a specific frequency component signal of the 1st signal and the 2nd signal from the 1st signal. CONSTITUTION:The leak current containing a component of low frequency f1 for measurement is detected by a synchronous detector MULT1 with the low frequency signal voltage to obtain the 1st signal. Further, the leak current is detected by an MULT2 with the voltage which is phase shifted by 90 deg. from the low frequency signal voltage to obtain the 2nd signal. Further, the frequency component of frequency 1/T in the 1st signal is detected and detected synchronously by an MULT3 with a signal having a repetitive period T to obtain a 3rd signal. The product of the 2nd and 3rd signals is found by a multiplier MT. A subtracter SUB subtracts the product of the 2nd and 3rd signals from the 1st signal to obtain an output which is not affected by a phase error.
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